Here's an English Treasury note, number 000001 which turned up on ebay back around 2004. This note is the third design.
The Treasury note issue was created in 1914 to replace gold coin in circulation as a response to a shortage of the coinage due to hoarding following the outbreak of world War 1.

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Treasury Note. One Pound, 1919. Signed N. F. Warren Fisher.

Here's what the British Museum website has to say about Treasury Notes.
The First World War (1914-18) placed great demands on Britain's gold supply: the Government needed gold to meet the costs of the war, and the public tended to hoard gold as private security in this time of uncertainty. This depleted the circulation of gold sovereigns and half sovereigns (coins worth one pound and ten shillings, respectively). To supplement the scarce coinage, the British Treasury began to issue paper notes for these amounts.
The first pound notes were issued on 7 August 1914, only three days after war was declared. Because they were produced in a such a hurry, the printing and design were very simple, and a more elegant note was issued in October 1914.
Later issues carried more elaborate designs, printed in colour with larger, patriotic images of St George and the Dragon and Britannia.
Treasury notes continued to be produced until 1928, when the Bank of England took over responsibility for issuing the one pound and ten shilling notes.

British Museum page is at the following address, which cannot be linked to, as it contains a £ symbol which breaks the link.
EDIT: Link removed—they moved or deleted the page. Museums which do that are very annoying!